1. Field of the Invention
The invention relates to a safety device used in systems for circulating a conductive fluid, especially ink-jet recovery circuits in continuous ink-jet printers.
2. Description of the Prior Art
A frequent problem lies in the need to check whether a flow of conductive fluid split-up in the form of drops within a pipe of small diameter is taking place under acceptable conditions which are conducive to good operation of the installation or on the contrary whether any irregularities have developed and justify remedial measures.
A problem of this nature arises particularly in the field of ink-jet printers. In fact, among the different ink-jet printing techniques, a certain number are based on the use of a continuous stream of ink drops from which part of the stream is withdrawn for the purpose of printing characters. The other drops are recycled in a special circuit known as a recirculation circuit. Now a key function of this device is the so-called "dump" zone for collecting the unused stream of drops to be recycled. Taking into account the nature of the inks employed which are capable by definition of very rapid drying and also taking into account the small cross-sectional area of the collecting element, blockage may eventually occur. Another potential danger lies in the possibility of failure of the pumping means. In all cases there is a risk of overflow of ink which would have a damaging effect on the installation. In order to avoid the consequences which would result from an operational fault condition of this type, it is a desirable objective to provide means for detecting such a fault condition in order to take the necessary steps without delay. And this is precisely the aim of the present invention.